1. Field of the Invention
The invention relates to a plasma display panel, and more particularly to a apparatus and method for burning a green sheet of a plasma display panel.
2. Description of the Related Art
FIG. 1 shows related equipment for burning a green sheet of a plasma display panel (PDP). The related burning equipment comprises: a feeding roller 1 that feeds the green sheet 5 to a PDP substrate 100; a tension roller 2 that imparts an appropriate tension to the green sheet such that the green sheet can be tightly drawn from the feeding roller 1; a heat and pressure roller 3 that heats and compresses the green sheet so as to bring the green sheet into intimate contact with the PDP substrate 100; and a plurality of conveying rollers 4 that convey the PDP substrate 100.
As the heat and pressure roller 3 compresses the green sheet 5 onto the PDP substrate 100, it heats the green sheet 5. Because of the increased temperature of the green sheet 5, solvent, a component of a binder, contained in the green sheet is transformed into a gas and then diffused at the surface of the green sheet.
The above process is repeatedly carried out as the PDP substrate 100 is conveyed by means of conveying rollers 4, so that the solvent present in the green sheet 5 is removed as the green sheet 5 is compressed onto the PDP substrate 100.
Typically, the green sheet 5 is about 10˜300 μm thick, which is a relatively high thickness, and contains a great amount of solvent. Because of the thickness and concentration of solvent, it is important to enhance the adhesive force between the “thick” green sheet and the PDP panel substrate, and to effectively remove the solvent from the green sheet such that the solvent does not remain in the green sheet.
Accordingly, the green sheet 5 is rapidly heated for a relatively short time, approximately 5 minutes or less, at a temperature range of approximately 100 to 200° C., within which the solvent can be actively volatized, by the heat and pressure roller 3 such that the solvent present in the green sheet 5 is rapidly removed therefrom, thereby preventing the green sheet film from being damaged due to overheating.
Related burning equipment is adapted to heat and compress the upper side of the green sheet 5 in order to bring the green sheet 5 into intimate contact with the PDP substrate 100 and to remove the solvent from the green sheet 5.
However, the solvent is generally concentrated on the lower surface of the green sheet 5 where the green sheet comes into intimate contact with the PDP substrate 100. Accordingly, the thermal energy generated by the heat and pressure roller 3, which heats the upper surface of the green sheet 5, does not sufficiently transfer to the lower portion of the green sheet 5. As a result, defects, such as bubbles, protrusions, film detachment and the like, are generated because of ineffective solvent removal and reduction in adhesive force between the green sheet and the PDP substrate during the burning process, thus lowering the productivity of the PDP manufacturing process.
In order to solve the problem described above, the prior art approaches have suggested that, after being heated to a temperature of about 100° C., the PDP substrate 100 is introduced into the burning equipment for the green sheet of the plasma display panel. However, using this method, there is a problem of damage to the green sheet caused by overheating.